Method of improving the color of cracked hydrocarbon distillates



Patented Feb. 14, 1939 UNITED STATES PATENT OFFICE METHOD OF IMPROVING THE COLOR OF CRACKED HYDROCARBON DISTILLATES No Drawing. Application June 25, 1936,

Serial No. 87,256

1 Claim.

This invention relates to the treatment of cracked hydrocarbon distillates and has to do particularly with a method and means for improving the color characteristicsof such distillates.

Uracked hydrocarbon distillates of the class of gasoline and kerosene often become discolored on storage as a result of the development of color bodies therein. This discoloration may be cleared up and the original color substantially restored by subjecting the off-colored distillate to the action of a suitable bleaching agent. Bleaching agents proposed heretofore, however, have been open to the objection that they are too slow in action or are incapable of maintaining the improved color.

It is the principal object of the present invention to provide an efficient and effective means of improving the color of cracked hydrocarbon dis-.

tillates and of stabilizing the color so that the improved color may be maintained.

In accordance with the present invention, the oil to be treated is subjected to the action of a powerful bleaching agent whereby the color is quickly improved and then the oil is stabilized by providing therein a stabilizing agent which will fix and maintain the improved color. The bleaching and stabilizing agents may both be added to the oil at the same time or the oil may be first bleached and then the stabilizing agent added. In general, the order of the addition of the reagents is not important although we prefer to add the stabilizing agent last.

The bleaching agents which we use in practicing the invention are the hydroxyl amines. Hydroxyl amine itself is useful although, due to its relative insolubility in gasoline, it is advantageous to use derivatives of hydroxyl amine, such as substituted hydroxyl amines; for example the alkyl or aryl derivatives. Included within the group of substituted compounds contemplated are alphaand and beta-.

beta-methylhydroxylamine, alphaphenylhydroxylamine and diphenylhydroxylamine. We prefer to use an alkyl hydroxylamine such as alpha-methy1hydroxylamine.

The stabilizing agents comprise the class of gum inhibitors including the hydroxy benzenes, the aliphatic and aromatic amines and aminophenols. Useful compounds are cresols, xylenols, pyrogallol, hydroquinone, catechol, orthoand para-aminophenols, benzyl-aminophenol, diphenylthiourea, lecithin, substituted phenylenediamines, dl-butylamine, tri-amylamine, etc. We prefer to use a polyhydroxy benzene, such as pyrcgallol or catechol or alkyl derivatives thereof, for example amylpyrogallol and tertiary-butylcatechol. Good results are obtained with diphenylthiourea, benzylaminophenol and lecithin.

As an example of the operation of the invention, a sample of cracked gasoline which had been in storage for some time and gone off-color to about 10 Saybolt was treated with about 0.01% of beta-phenylhydroxylamine. The color was bleached in a few minutes to +19 Saybolt. The restored color in the course of a few weeks normally reverted slowly but on the addition of about 0.01% of amyl pyrogallol the color may be substantially fixed. As another example, a cracked gasoline which originally had a Saybolt color of around 20 had gone off-color in the course of a few months to yellow. To this off-color sample was added about 0.01% of alpha-methylhydroxylamine. In the course of a few hours the color was restored to approximately the original. The sample having the improved color normally tended to become slowly discolored after a few months storage. By the addition of about 0.01% of diphenylthiourea, the improved color may be substantially maintained.

The amounts of bleaching and stabilizing agents given in the above examples are not'flxed and may be varied within quite wide limits. In

general, amounts varying from about 0.005-0.10%

may be used and preferably betweenabout 0.005 and 0.05%.

The present invention has the advantage that a powerful bleaching agent may be used, thereby conserving time and improving the color to a LOUIS A. CLARKE. JOHN R. CALLAWAY. 

